Powder material for three-dimensional object formation, hardening liquid and three-dimensional object formation kit, and formation method and formation apparatus of three-dimensional object

ABSTRACT

Provided is a three-dimensional object formation method for forming a three-dimensional object by at least repeating: forming a powder material layer using a powder material for three-dimensional object formation containing a base material coated with an organic material; and hardening a predetermined region of the powder material layer by delivering a hardening liquid to the powder material layer formed in the formation of a powder material layer, where the hardening liquid contains a cross-linking agent cross-linkable with the organic material.

TECHNICAL FIELD

The present invention relates to a powder material for three-dimensionalobject formation, a hardening liquid, and a three-dimensional objectformation kit, and a formation method and a formation apparatus of athree-dimensional object, which enable easy and efficient formation of acomplex three-dimensional object.

BACKGROUND ART

Recently, there have been increasing needs for small-lot production ofcomplex minute three-dimensional objects. A powder sintering method, apowder binding method, etc. have been proposed as techniques forcatering to the needs (see PTL 1 to PTL 3).

The powder sintering method is a method of forming a powder thin layer,irradiating the thin layer with laser light to form a thin sinteredproduct, repeating these steps to stack thin sintered productssequentially over the thin sintered product to thereby obtain a desiredthree-dimensional object. The powder binding method is a method ofhardening a powder thin layer using an adhesive material instead ofperforming laser sintering as in the powder sintering method, andstacking such thin layers to thereby obtain a desired three-dimensionalobject.

As the powder binding method, for example, there are proposed a methodof supplying an adhesive material to a powder thin layer according to aninkjet method, a method of stacking layers of a powder material in whichpowder particles and adhesive particles are mixed, delivering a bindingagent thereto to dissolve the adhesive material particles, andsolidifying them to thereby form a three-dimensional object (see PTL 4),and a method of dissolving a powder material in which a base materialsuch as glass and ceramic is coated with a hydrophobic resin, and aresin coated with a hydrophobic solvent such as limonene, andsolidifying them to thereby form a three-dimensional object (see PTL 5).

CITATION LIST Patent Literature

PTL 1 Japanese Patent Application Laid-Open (JP-A) No. 2000-328106

PTL 2 JP-A No. 2006-200030

PTL 3 JP-A No. 2003-48253

PTL 4 JP-A No. 2004-330743

PTL 5 JP-A No. 2005-297325

PTL 6 U.S. Pat. No. 7,049,363

SUMMARY OF INVENTION Technical Problem

However, in the case of supplying the adhesive material according to aninkjet method, there are problems that the nozzle head used may beclogged, selection of adhesive materials that can be used is limited,cost efficiency is poor, etc.

Further, there is a problem in the technique described in PTL 4 that itis difficult to impart a sufficient strength and precision to athree-dimensional object because even though the adhesive particles aresupplied with a binding material and dissolved, the obtained dissolvedadhesive solution tends not to spread uniformly between the powderparticles.

According to the technique described in PTL 5, limonene has a lowvolatility and may tend to remain in a three-dimensional object andreduce the strength thereof. Further, a low volatility solvent such astoluene has a problem in safety. Furthermore, in order for the materialto be bound together only at the coating resin, it is necessary toprovide the coating resin film with a large thickness (it is necessaryto use the resin in a large amount). Therefore, there are problems thata three-dimensional object to be obtained may not have a sufficientprecision, and that the density of the base material in thethree-dimensional object may be low. Particularly, in the case of ametal sintered object or a ceramic sintered object, in which case, theresin is removed finally for a post-treatment such as sintering, theinability to make the density of the base material sufficiently highmakes the problems with the strength and precision of the sinteredobject remarkable.

PTL 6 proposes, as a material usable in 3D printing, particles composedof a liquid as a first constituent element, and a binder soluble in theliquid as a second constituent element. The literature disclosesaddition of a polymerization initiator such as a peroxide to the liquidor the binder. However, because of its characteristic of undergoing aspontaneous decomposition under heat or light to produce radicals andthereby initiate a reaction, a polymerization initiator such as aperoxide decomposes under heat and light environmental conditions andbecomes inactive. Therefore, there is a problem that a liquid containingsuch a polymerization initiator has a poor storage stability.

Hence, the present invention aims to solve the conventional problemsdescribed above and achieve the following object. That is, an object ofthe present invention is to provide a three-dimensional object formationmethod that can form a three-dimensional object having a complexstereoscopic (three-dimensional (3D)) shape easily and efficiently byusing a powder material of a metal, etc., without causing a shapecollapse before sintering, etc., and with a dimensional precision.

Solution to Problem

A solution to the problems described above is as follows.

A three-dimensional object formation method of the present inventionincludes forming a three-dimensional object by at least repeating thesteps of:

forming a powder material layer using a powder material forthree-dimensional object formation containing a base material coatedwith an organic material; and

hardening a predetermined region of the powder material layer bydelivering a hardening liquid containing a cross-linking agentcross-linkable with the organic material to the powder material layerformed in the formation of a powder material layer.

In the three-dimensional object formation method of the presentinvention, a powder material layer is formed with a powder material forthree-dimensional object formation containing a base material coatedwith an organic material in the step of forming a layer of a powdermaterial for three-dimensional object formation. Then, a hardeningliquid containing a cross-linking agent cross-linkable with the organicmaterial is delivered to the powder material layer formed in the step offorming a powder material layer in the step of hardening the powdermaterial layer in order to harden a predetermined region of the powdermaterial layer. That is, the powder material for three-dimensionalobject formation contains the base material coated with the organicmaterial. When the hardening liquid is delivered to the organicmaterial, the organic material is dissolved and cross-linked by theeffect of the cross-linking agent contained in the hardening liquid, tothereby form a three-dimensional network. Therefore, the layer of thepowder material for three-dimensional object formation is hardened witha dimensional precision and a favorable strength.

Through repetition of these steps, a complex three-dimensional object isformed easily, efficiently, without shape collapse before sintering,etc., and with a dimensional precision. As the obtainedthree-dimensional object has a favorable strength, it does not undergo ashape collapse even when it is held in a hand or air-blown in order forexcess powder material for three-dimensional object formation to beremoved, and afterwards, can be subjected to sintering, etc. with ease.In the three-dimensional object, the base material is present densely(at a high filling rate), and the organic material is present onlyslightly around the base material particles. Therefore, when a compact(a sintered object) is obtained through the afterward sintering, etc.,the obtained compact includes few unnecessary voids, and a compact(sintered object) having a beautiful appearance can be obtained.

A powder material for three-dimensional object formation of the presentinvention is a powder material for three-dimensional object formationused in the three-dimensional object formation method of the presentinvention, and contains the base material coated with the organicmaterial.

In the powder material for three-dimensional object formation of thepresent invention, the organic material coating the base material can bedissolved and made cross-linkable by the effect of the hardening liquid.Therefore, when the hardening liquid is delivered to the organicmaterial, the organic material is dissolved and cross-linked by theeffect of the cross-linking agent contained in the hardening liquid.Hence, when a thin layer is formed with the powder material forthree-dimensional object formation of the present invention and thehardening liquid is activated on the thin layer, the thin layer ishardened.

A hardening liquid of the present invention is a hardening liquid usedin the three-dimensional object formation method of the presentinvention, and contains a cross-linking agent cross-linkable with theorganic material.

According to the hardening liquid of the present invention, when thehardening liquid is delivered to the organic material, the organicmaterial is dissolved and cross-linked by the effect of thecross-linking agent contained in the hardening liquid.

The “cross-linking agent” of the present invention means a compound thathas a site cross-linking-reactive with a functional group ofcross-linking targets (organic materials such as a polymer, etc.), andby a cross-linking reaction, itself becomes the constituent element ofthe bonding portion of a cross-linking bond between cross-linkingtargets. Hence, the cross-linking agent is conceptually different from aso-called “initiator” such as a peroxide (organic peroxide) and areducing substance that does not itself become the constituent elementof a cross-linking bonding portion but initiates or promotes a radicalreaction by undergoing a spontaneous decomposition under heat or lightto thereby produce free radicals, adding to an unsaturated monomer,opening a double bond and simultaneously causing a new radical reaction,and repeating these processes to thereby promote polymerization, or bywithdrawing hydrogen atoms bonded with carbon atoms of saturatedcompounds to produce new radicals and let these radicals recombine tothereby form a bridge between these saturated compounds. The“cross-linking agent” of the present invention is clearly distinguishedfrom the initiator.

A three-dimensional object formation kit contains the powder materialfor three-dimensional object formation of the present invention and thehardening liquid of the present invention.

A three-dimensional object formation apparatus of the present inventionincludes:

a powder material layer forming unit configured to form a layer of apowder material for three-dimensional object formation containing a basematerial coated with an organic material;

a hardening liquid delivering unit configured to deliver a hardeningliquid containing a cross-linking agent cross-linkable with the organicmaterial in order to harden a predetermined region of the layer of thepowder material for three-dimensional object formation formed by thepowder material layer forming unit;

a powder material containing unit containing the powder material forthree-dimensional object formation; and

a hardening liquid containing unit containing the hardening liquid.

Advantageous Effects of Invention

The present invention can provide a three-dimensional object formationmethod that can solve the conventional problems described above, and canform a three-dimensional object having a complex stereoscopic(three-dimensional (3D)) shape easily and efficiently by using a powdermaterial of a metal, etc., without causing a shape collapse beforesintering, etc., and with a dimensional precision.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing an example of a powder stackformation apparatus of the present invention.

FIG. 2 is a schematic diagram showing another example of a powder stackformation apparatus of the present invention.

DESCRIPTION OF EMBODIMENTS

(Powder Material for Three-Dimensional Object Formation)

A powder material for three-dimensional object formation of the presentinvention contains a base material coated with an organic material, andfurther contains other components, etc. according to necessity. Thematerial coating the base material is principally an organic material,but may contain an inorganic material according to necessity.

The powder material for three-dimensional object formation is used in athree-dimensional object formation method of the present inventiondescribed later.

—Base Material—

The base material is not particularly limited, and an arbitrary basematerial may be selected according to the purpose as long as it has ashape of a powder or particles. Examples thereof include metal,ceramics, carbon, polymer, wood, a material having affinity to a livingbody, and sand. In terms of obtaining a three-dimensional object havinga high strength, metal, ceramics, etc. that can be finally subjected tosintering are preferable.

Preferable examples of the metal include stainless (SUS) steel, iron,copper, titanium, and silver. Examples of the stainless (SUS) steelinclude SUS 316L.

Examples of the ceramics include metal oxide. Specific examples includesilica (SiO₂), alumina (Al₂O₃), zirconia (ZrO₂), and titania (TiO₂).

Examples of the carbon include graphite, graphene, carbon nanotube,carbon nanohorn, and fullerene.

Examples of the polymer include a publicly-known resin insoluble towater.

Examples of the wood include wooden chip and cellulose.

Examples of the material having affinity to a living body includepolylactic acid and calcium phosphate.

One of these materials may be used alone, or two or more of these may beused in combination.

In the present invention, commercially available particles or powdermade from these materials may be used as the base material.

Examples of the commercially available product include SUS 316L (PSS316Lmanufactured by Sanyo Special Steel Co., Ltd.), SiO₂ (ECCERICA SE-15Kmanufactured by Tokuyama Corporation), AlO₂ (TAIMICRON TM-5 Dmanufactured by Taimei Chemicals Co., Ltd.), and ZrO₂ (TZ-B53manufactured by Tosoh Corporation).

The base material may be subjected to a publicly-known surface(reforming) treatment with a view to increasing affinity to the organicmaterial, etc.

The average particle diameter of the base material is not particularlylimited and may be appropriately selected according to the purpose.However, it is preferably from 0.1 μm to 500 μm, more preferably from 5μm to 300 μm, and yet more preferably from 15 μm to 250 μm.

When the average particle diameter is from 0.1 μm to 500 μm, theformation efficiency of a three-dimensional object is good, andtreatability and a handling property of a three-dimensional object aregood. When the average particle diameter is 500 μm or less, a rate atwhich a thin layer is filled with the powder material forthree-dimensional object formation is good when a thin layer is formedwith the powder material for three-dimensional object formation, andvoids or the like are hardly produced in a three-dimensional object tobe obtained.

The average particle diameter of the base material can be measured witha publicly-known particle size meter, e.g., MICROTRACK HRA (manufacturedby Nikkiso Co, Ltd.), according to a publicly-known method.

The particle size distribution of the base material is not particularlylimited and may be appropriately selected according to the purpose.

The contour, surface area, circularity, fluidity, wettability, etc. ofthe base material may be appropriately selected according to thepurpose.

—Organic Material—

It is only necessary that the organic material dissolve in a hardeningliquid and have a property of being able to be cross-linked by theeffect of a cross-linking agent contained in the hardening liquid.

In the present invention, the organic material is said to havesolubility when 1 g of the organic material is mixed in 100 g of asolvent constituting a hardening liquid having a temperature of 30° C.and stirred, and 90% by mass or greater of the organic material isdissolved.

The viscosity of the organic material when it is in the form of a 4% bymass (w/w %) solution having a temperature of 20° C. is preferably 40mPa·s or lower, more preferably from 1 mPa·s to 35 mPa·s, andparticularly preferably from 5 mPa·s to 30 mPa·s.

When the viscosity is 40 mPa·s or lower, a strength of a hardened object(a three-dimensional object) made from (a layer) of the powder materialfor three-dimensional object formation formed by delivering thehardening liquid to the powder material for three-dimensional objectformation is improved, and it becomes harder for the hardened object toundergo a problem of shape collapse or the like in an afterwardtreatment or handling such as sintering, and a dimensional precision ofa hardened object (a three-dimensional object) made from (a layer) ofthe powder material for three-dimensional object formation formed bydelivering the hardening liquid to the powder material forthree-dimensional object formation tends to be improved.

The viscosity can be measured according to, for example, JIS K7117.

The organic material is not particularly limited, but is preferablywater-soluble in terms of treatability, environmental hazardousness,etc. Examples thereof include a water-soluble resin, and a water-solubleprepolymer. When a powder material for three-dimensional objectformation uses such a water-soluble organic material, an aqueous mediumcan be used as the medium of the hardening liquid likewise. Further,when disposing of or recycling the powder material, it is easy toseparate the organic material and the base material from each other witha water treatment.

Examples of the water-soluble resin include a polyvinyl alcohol resin, apolyacrylic acid resin, a cellulose resin, starch, gelatin, a vinylresin, an amide resin, an imide resin, an acrylic resin, andpolyethylene glycol.

These may be a homopolymer or a heteropolymer (a copolymer), may bemodified or have a publicly-known functional group introduced, or may bein the form of a salt, as long as they have the water-solubilitydescribed above.

Hence, when the water-soluble resin is the polyvinyl alcohol resin, itmay be polyvinyl alcohol or polyvinyl alcohol modified with anacetoacetyl group, an acetyl group, silicone, or the like (acetoacetylgroup-modified polyvinyl alcohol, acetyl group-modified polyvinylalcohol, silicone-modified polyvinyl alcohol, or the like), or may be abutanediol/vinyl alcohol copolymer or the like. When the water-solubleresin is the polyacrylic acid resin, it may be a polyacrylic acid or maybe a salt such as sodium polyacrylate. When the water-soluble resin isthe cellulose resin, it may be cellulose, or may be carboxymethylcellulose (CMC) or the like. When the water-soluble resin is the acrylicresin, it may be polyacrylic acid, an acrylic acid/maleic anhydridecopolymer, or the like.

Examples of the water-soluble prepolymer include an adhesivewater-soluble isocyanate prepolymer contained in a water sealant.

Examples of organic materials and resins that are not water-solubleinclude acrylic, maleic acid, silicone, butyral, polyester, polyvinylacetate, a vinyl chloride/vinyl acetate copolymer, polyethylene,polypropylene, polyacetal, an ethylene/vinyl acetate copolymer, anethylene/(meth)acrylic acid copolymer, an α-olefin/maleicanhydride-based copolymer, an esterified α-olefin/maleic anhydride-basedcopolymer, polystyrene, poly(meth)acrylic acid ester, an α-olefin/maleicanhydride/vinyl group-containing monomer copolymer, a styrene/maleicanhydride copolymer, a styrene/(meth)acrylic acid ester copolymer,polyamide, an epoxy resin, a xylene resin, a ketone resin, a petroleumresin, rosin or a derivative thereof, a coumarone-indene resin, aterpene resin, a polyurethane resin, a styrene/butadiene rubber,polyvinyl butyral, a synthetic rubber such as a nitrile rubber, anacrylic rubber, and an ethylene/propylene rubber, and nitrocellulose.

In the present invention, an organic material having a cross-linkablefunctional group is preferable among the examples of the organicmaterial. The cross-linkable functional group is not particularlylimited, and an arbitrary cross-linkable functional group may beselected according to the purpose. Examples thereof include a hydroxylgroup, an amide group, a phosphoric group, a thiol group, an acetoacetylgroup, and an ether bond.

It is preferable that the organic material have a cross-linkablefunctional group, because this makes it easy for the organic material tobe cross-linked and form a hardened object (a three-dimensional object).Among such organic materials, a polyvinyl alcohol resin having anaverage degree of polymerization of from 400 to 1,100 is preferable.Furthermore, a modified polyvinyl alcohol resin having a cross-linkablefunctional group introduced into the molecule as described above ispreferable. An acetoacetyl group-modified polyvinyl alcohol resin isparticularly preferable. For example, when a polyvinyl alcohol resin hasan acetoacetyl group, a metal in the cross-linking agent contained inthe hardening liquid greatly assists a bending strength of theacetoacetyl group, which can hence easily form a complexthree-dimensional network structure (a cross-linked structure) via themetal.

One kind of an acetoacetyl group-modified polyvinyl alcohol resin may beused, or two or more kinds of acetoacetyl group-modified polyvinylalcohol resins having different properties such as viscosity andsaponification degree may be used in combination. It is more preferableto use acetoacetyl group-modified polyvinyl alcohol resins having anaverage degree of polymerization of from 400 to 1,100.

As the organic material, one kind of an organic material may be usedalone, or two or more kinds of organic materials may be used incombination. The organic material may be an appropriately synthesizedproduct or may be a commercially available product.

Examples of the commercially available product include polyvinylalcohols (PVA-205C and PVA-220C manufactured by Kuraray Co., Ltd.), apolyacrylic acid (JULIMER AC-10 manufactured by Toagosei Co., Ltd.), asodium polyacrylate (JULIMER AC-103P manufactured by Toagosei Co.,Ltd.), an acetoacetyl group-modified polyvinyl alcohol (GOHSENX Z-300,GOHSENX Z-100, GOHSENX Z-200, GOHSENX Z-205, GOHSENX Z-210, and GOHSENXZ-220 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), acarboxy group-modified polyvinyl alcohol (GOHSENX T-330, GOHSENX T-350,and GOHSENX T-330T manufactured by Nippon Synthetic Chemical IndustryCo., Ltd.), a butanediol/vinyl alcohol copolymer (NICHIGO G-POLYMEROKS-8041 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.),a carboxymethyl cellulose sodium (CELLOGEN 5A and CELLOGEN 6Amanufactured by Daiichi Kogyo Seiyaku Co., Ltd.), starch (HISTARD PSS-5manufactured by Sanwa Starch Co., Ltd.), and gelatin (BEMATRIX GELATINmanufactured by Nitta Gelatin Inc.).

The coating thickness of the organic material on the base material ispreferably from 5 nm to 1,000 nm, more preferably from 5 nm to 500 nm,yet more preferably from 50 nm to 300 nm, and particularly preferablyfrom 100 nm to 200 nm on an average thickness basis.

Because the present invention utilizes a hardening effect by means of across-linking agent, the coating thickness can be made smaller than inconventional techniques, and a strength and a precision can both besatisfied even with a thin film.

When the average thickness as the coating thickness is 5 nm or greater,a hardened object (a three-dimensional object) made of (a layer of) thepowder material for three-dimensional object formation formed bydelivering the hardening liquid to the powder material forthree-dimensional object formation can be enhanced in the strength, anddoes not undergo problems of shape collapse or the like during anafterward treatment or handling such as sintering. When the averagethickness is 1,000 nm or less, a hardened object (a three-dimensionalobject) made of (a layer of) the powder material for three-dimensionalobject formation formed by delivering the hardening liquid to the powdermaterial for three-dimensional object formation can be enhanced in thedimensional precision.

The average thickness can be measured by, for example, embedding thepowder material for three-dimensional object formation in an acrylicresin or the like, exposing a surface of the base material by etching orthe like, and then using a scanning tunnel microscope (STM), an atomicforce microscope (AFM), a scanning electron microscope (SEM), or thelike.

The coverage (area ratio) at which the surface of the base material iscovered with the organic material is not particularly limited and may beappropriately selected according to the purpose. However, it ispreferably 15% or greater, more preferably 50% or greater, andparticularly preferably 80% or greater.

When the coverage is 15% or greater, a hardened object (athree-dimensional object) made of (a layer of) the powder material forthree-dimensional object formation formed by delivering the hardeningliquid to the powder material for three-dimensional object formation canhave a sufficient strength, and does not undergo problems of shapecollapse or the like during an afterward treatment or handling such assintering, or a hardened object (a three-dimensional object) made of (alayer of) the powder material for three-dimensional object formationformed by delivering the hardening liquid to the powder material forthree-dimensional object formation can be enhanced in the dimensionalprecision.

For the coverage, a photograph of the powder material forthree-dimensional object formation may be observed, and based on thepowder material for three-dimensional object formation captured in thetwo-dimensional photograph, an average ratio (%) of an area of a portionof each particle of the powder material for three-dimensional objectformation that is covered with the organic material to the whole area ofthe surface of the particle may be calculated as the coverage.Alternatively, the coverage may be measured by performing elementalmapping of the portion covered with the organic material according toenergy dispersive X-ray spectrometry such as SEM-EDS.

—Other Components—

The other components are not particularly limited, and arbitrarycomponents may be selected according to the purpose. Examples thereofinclude a fluidizer, a filler, a leveling agent, and a sintering aid. Itis preferable that the powder material for three-dimensional objectformation contain the fluidizer, because this makes it possible to forma layer or the like of the powder material for three-dimensional objectformation easily and efficiently. It is preferable that the powdermaterial for three-dimensional object formation contain the filler,because this makes it harder for voids or the like to be produced in ahardened object (a three-dimensional object) to be obtained. It ispreferable that the powder material for three-dimensional objectformation contain the leveling agent, because this improves thewettability of the powder material for three-dimensional objectformation and makes handling or the like easy. It is preferable that thepowder material for three-dimensional object formation contain thesintering aid, because when a hardened object (a three-dimensionalobject) to be obtained is subjected to a sintering treatment, it can besintered at a lower temperature.

—Production of Powder Material for Three-Dimensional Object Formation—

A method for producing the powder material for three-dimensional objectformation is not particularly limited, and an arbitrary method may beselected according to the purpose. Examples thereof include a method ofcoating the base material with the organic material according to apublicly-known coating method.

A method for coating a surface of the base material with the organicmaterial is not particularly limited, and an arbitrary method may beselected from publicly-known coating methods. Examples of such coatingmethods include a rolling fluidized coating method, a spray dryingmethod, a stirring mixing adding method, a dipping method, and a kneadercoating method. These coating methods can be practiced withpublicly-known commercially available coating machines, a granulatingmachine, etc.

—Physical Properties, Etc. Of Powder Material for Three-DimensionalObject Formation—

The average particle diameter of the powder material forthree-dimensional object formation is not particularly limited and maybe appropriately selected according to the purpose. However, it ispreferably from 3 μm to 250 μm, more preferably from 3 μm to 200 μm, yetmore preferably from 5 μm to 150 and particularly preferably from 10 μmto 85 μm.

When the average particle diameter is 3 μm or greater, the powdermaterial can have a good fluidity, a layer of the powder material can beformed easily, and a surface of a stacked layer can have a goodsmoothness. This tends to improve the formation efficiency of athree-dimensional object, improve treatability and a handling property,and improve a dimensional precision. When the average particle diameteris 250 μm or less, particles of the powder material have little roombetween them, which provides a low voidage in an object to be obtainedand contributes to enhancement of the strength. Therefore, a preferablerange of the average particle diameter for satisfying both of adimensional precision and a strength is from 3 μm to 250 μm.

The particle size distribution of the powder material forthree-dimensional object formation is not particularly limited and maybe appropriately selected according to the purpose.

As a property of the powder material for three-dimensional objectformation, an angle of repose thereof is preferably 60 degrees or less,more preferably 50 degrees or less, and yet more preferably 40 degreesor less.

When the angle of repose is 60 degrees or less, the powder material forthree-dimensional object formation can be placed at a desired positionof a support member efficiently and stably.

The angle of repose can be measured with, for example, a powdercharacteristic measurement instrument (POWDER TESTER TYPE PT-Nmanufactured by Hosokawa Micron Inc.).

The powder material for three-dimensional object formation of thepresent invention can be favorably used for easy and efficient formationof various compacts and structures, and can be particularly favorablyused for a three-dimensional object formation kit of the presentinvention, the hardening liquid of the present invention, athree-dimensional object formation method of the present invention, anda three-dimensional object formation apparatus of the present inventionto be described later.

A structure having a complex three-dimensional shape can be formedeasily, efficiently, and dimensionally precisely, only by delivering thehardening liquid of the present invention to the powder material forthree-dimensional object formation of the present invention. A structureobtained in this way is a hardened object (a three-dimensional object)having a sufficient hardness, and excellent in treatability and ahandling property without undergoing a shape collapse when held in ahand, set in or out from a mold, or air-blown in order for excess powdermaterial for three-dimensional object formation to be removed. Thehardened object may be used as is, or, as a hardened object to besintered, may further be subjected to a sintering treatment to be formedas a compact (a sintered compact of the three-dimensional object). Whenit is subjected to a sintering treatment, no unnecessary voids may beproduced in the compact to be obtained after the sintering, and acompact with a beautiful appearance can be obtained easily.

(Hardening Liquid)

The hardening liquid of the present invention is a hardening liquid usedin the three-dimensional object formation method of the presentinvention, contains a cross-linking agent cross-linkable with theorganic material, contains a medium (solvent) for dissolving the organicmaterial and a component for promoting the dissolution, and furthercontains other components according to necessity.

When the hardening liquid is delivered to the organic material, theorganic material is dissolved and cross-linked by the effect of thecross-linking agent contained in the hardening liquid.

—Medium—

The medium is not particularly limited except that it should be able todissolve the organic material coating the base material. Examples of themedium include: an aqueous medium such as water, alcohol such asethanol, ether, and ketone; an ether-based solvent such as aliphatichydrocarbon, and glycol ether; an ester-based solvent such as ethylacetate; a ketone-based solvent such as methyl ethyl ketone; and ahigher alcohol. Among these, an aqueous medium is preferable and wateris more preferable in terms of environmental hazardousness anddischarging stability when delivering the hardening liquid according toan inkjet method (i.e., temporal viscosity change should be little). Theaqueous medium may be water that contains any other component than watersuch as alcohol in a small amount. Further, when the medium of thehardening liquid is an aqueous medium, it is preferable that the organicmaterial principally contain a water-soluble organic material.

—Cross-Linking Agent—

The cross-linking agent is not particularly limited, and an arbitrarycross-linking agent may be selected according to the purpose as long asit has a property of being able to cross-link the organic material.Examples thereof include a metal salt, a metal complex, a zirconia-basedcross-linking agent, a titanium-based cross-linking agent, awater-soluble organic cross-linking agent, and a chelating agent.

Examples of the zirconia-based cross-linking agent include zirconiumoxychloride, and ammonium zirconium carbonate.

Examples of the titanium-based cross-linking agent include titaniumacylate, and titanium alkoxide.

Examples of the water-soluble organic cross-linking agent include acarbodiimide group-containing compound, and a bis-vinyl sulfonecompound.

Examples of the chelating agent include an organic titanium chelate, andan organic zirconia chelate.

One of these may be used alone, or two or more of these may be used incombination. Among these, a metal salt is more preferable.

Preferable examples of the metal salt include a metal salt that ionizesa divalent or higher cationic metal in water. Preferable specificexamples thereof include zirconium oxychloride octahydrate(tetravalent), aluminum hydroxide (trivalent), magnesium hydroxide(divalent), a titanium lactate ammonium salt (tetravalent), basicaluminum acetate (trivalent), an ammonium salt of zirconium carbonate(tetravalent), titanium triethanol aminate (tetravalent), a glyoxylicacid salt and a zirconium lactate ammonium salt.

These may be commercially available products. Examples of commerciallyavailable products include zirconium oxychloride octahydrate (zirconiumoxychloride manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.),aluminum hydroxide (manufactured by Wako Pure Chemical Industries,Ltd.), magnesium hydroxide (manufactured by Wako Pure ChemicalIndustries, Ltd.), a titanium lactate ammonium salt (ORGATIX TC-300manufactured by Matsumoto Fine Chemical Co., Ltd.), a zirconium lactateammonium salt (ORGATIX ZC-300 manufactured by Matsumoto Fine ChemicalCo., Ltd.), basic ammonium acetate (manufactured by Wako Pure ChemicalIndustries Ltd.), a bis-vinyl sulfone compound (VS-B (K-FJC)manufactured by Fuji Fine Chemical Co., Ltd.), an ammonium salt ofzirconium carbonate (ZIRCOZOL AC-20 manufactured by Daiichi KigensoKagaku Kogyo Co., Ltd.), titanium triethanol aminate (ORGATIX TC-400manufactured by Matsumoto Fine Chemical Co., Ltd.), a glyoxylic acidsalt (SAFELINK SPM-01 manufactured by Nippon Synthetic Chemical IndustryCo., Ltd.), and adipic acid dihydrazide (manufactured by Otsuka ChemicalCo., Ltd.). It is preferable that the metal of the metal salt have avalence of 2 or greater, because this can improve the cross-linkingstrength, and provide a favorable strength to the three-dimensionalobject to be obtained.

A lactic acid ion is preferable as a ligand of the cationic metal,because it is excellent in discharging stability (temporal storagestability) of the hardening liquid.

A cross-linking agent in which the ligand of the cationic metal is acarbonic acid ion, such as zirconium ammonium carbonate, produces aself-polymerization reaction in an aqueous solution, which makes iteasier for the properties of the cross-linking agent to change.Therefore, in terms of discharging stability, it is preferable to use across-linking agent in which the ligand of the cationic metal is alactic acid ion. However, addition of a chelating agent such as agluconic acid and triethanol amine can suppress the self-polymerizationreaction of zirconium ammonium carbonate in an aqueous solution, and canimprove discharging stability.

—Other Components—

As the other components, arbitrary components may be selected dependingon various conditions such as the type of the unit configured to deliverthe hardening liquid, frequency and amount of use, etc. For example,when the hardening liquid is delivered according to an inkjet method, acomponent may be selected depending on the influence on a nozzle head ofan inkjet printer or the like, such as clogging. Examples of the othercomponents include a preservative, an antiseptic agent, a stabilizingagent, and a pH adjustor.

A method for preparing the hardening liquid is not particularly limited,and an arbitrary method may be selected according to the purpose.Examples thereof include a method of adding and mixing the cross-linkingagent, and according to necessity, the other components in the aqueousmedium, and dissolving them therein.

The content (concentration) of the cross-linking agent in the hardeningliquid is not particularly limited, and may be appropriately selectedaccording to the purpose. However, it is preferably a concentration atwhich the cross-linking agent is from 0.1 parts by mass to 50 parts bymass (% by mass), more preferably a concentration at which thecross-linking agent is from 0.5 parts by mass to 40 parts by mass (% bymass), and particularly preferably from 1 part by mass to 35 parts bymass (% by mass), relative to 100 parts by mass of the organic material.

When the concentration is 0.1% by mass or higher, a hardened object (athree-dimensional object) made of (a layer of) the powder material forthree-dimensional object formation formed by delivering the hardeningliquid to the powder material for three-dimensional object formation canbe enhanced in the strength, and does not undergo problems of shapecollapse or the like during an afterward treatment or handling such assintering. When the concentration is 50% by mass or lower, a hardenedobject (a three-dimensional object) made of (a layer of) the powdermaterial for three-dimensional object formation formed by delivering thehardening liquid to the powder material for three-dimensional objectformation can be enhanced in the dimensional precision.

(Three-Dimensional Object Formation Kit)

A three-dimensional object formation kit of the present inventionincludes the powder material for three-dimensional object formation ofthe present invention, and the hardening liquid of the presentinvention, and further includes other components according to necessity.

In the three-dimensional object formation kit of the present invention,the cross-linking agent needs not be contained in the hardening liquid,but may be included in the form of a solid. The kit may be provided soas to allow the cross-linking agent to be mixed with an aqueous mediumand prepared as the hardening liquid, in use.

The three-dimensional object formation kit of the present invention canbe favorably used for formation of various compacts and structures, andcan be particularly favorably used for a three-dimensional objectformation apparatus of the present invention and a three-dimensionalobject to be obtained according to the present invention, which are tobe described later.

When a structure is formed with the three-dimensional object formationkit of the present invention, a structure having a complexthree-dimensional shape can be formed easily, efficiently, anddimensionally precisely, only by activating the hardening liquid on thepowder material for three-dimensional object formation and drying themif necessary. The structure obtained in this way is a hardened object (athree-dimensional object) having a sufficient hardness, and excellent intreatability and a handling property without undergoing a shape collapsewhen held in a hand, set in or out from a mold, or air-blown in orderfor excess powder material for three-dimensional object formation to beremoved. The hardened object may be used as is, or, as a hardened objectto be sintered, may further be subjected to a sintering treatment to beformed as a compact (a sintered compact of the three-dimensionalobject). When it is subjected to a sintering treatment, no unnecessaryvoids may be produced in the compact to be obtained after the sintering,and a compact with a beautiful appearance can be obtained easily.

<Three-Dimensional Object>

A three-dimensional object to be obtained according to the presentinvention is either of a hardened object obtained by delivering thehardening liquid of the present invention to the powder material forthree-dimensional object formation of the present invention describedabove, and a hardened object obtained by using the three-dimensionalobject formation kit of the present invention described above, anddelivering the hardening liquid included in the three-dimensional objectformation kit to the powder material for three-dimensional objectformation included therein, and is used as a hardened object to besintered, which is for forming a compact (a sintered compact of thethree-dimensional object) by sintering.

The three-dimensional object is an object obtained only by deliveringthe hardening liquid to the powder material for three-dimensional objectformation, but has a sufficient strength. In the three-dimensionalobject, the base material is present densely (at a high filling rate),and the organic material is present only slightly around the basematerial particles. Therefore, when a compact (a sintered compact) isobtained through the afterward sintering, etc., the obtained compactincludes no unnecessary voids (marks of wax removal) because the amountof organic components to be volatilized (the amount of wax to beremoved) can be suppressed unlike in a hardened object made of aconventional powder or particles using an adhesive or the like, and acompact (sintered compact) having a beautiful appearance can beobtained.

The strength of the three-dimensional object is, for example, such alevel at which the object would not undergo a shape collapse or the likewhen the surface of the object is scrubbed, and a level at which itwould not have a crack or the like when it is air-blown with an air gunwith a nozzle caliber of 2 mm and an air pressure of 0.3 mPa, from adistance of 5 cm away.

(Formation Method and Formation Apparatus of Three-Dimensional Object)

A three-dimensional object formation method of the present inventionincludes a powder material layer forming step and a powder materiallayer hardening step, and further includes other steps such as asintering step according to necessity.

The method is characterized by forming a three-dimensional object byrepeating the powder material layer forming step and the powder materiallayer hardening step.

A three-dimensional object formation apparatus of the present inventionincludes a powder material layer forming unit, a hardening liquiddelivering unit, a powder material containing unit containing a powdermaterial, and a hardening liquid containing unit containing a hardeningliquid, and further includes other units such as a hardening liquidsupplying unit and a sintering unit according to necessity.

—Powder Material Layer Forming Step and Powder Material Layer FormingUnit—

The powder material layer forming step is a step of using a powdermaterial for three-dimensional object formation containing a basematerial coated with an organic material, and forming a layer of thepowder material.

The powder material layer forming unit is a unit configured to use apowder material for three-dimensional object formation containing a basematerial coated with an organic material, and form a layer of the powdermaterial.

It is preferable that the layer of the powder material forthree-dimensional object formation be formed over a support member.

—Support Member—

The support member is not particularly limited, and an arbitrary supportmember may be selected according to the purpose as long as the powdermaterial for three-dimensional object formation can be placed over it.Examples thereof include a table having a surface over which to placethe powder material for three-dimensional object formation, and a baseplate included in an apparatus shown in FIG. 1 of JP-A No. 2000-328106.

A surface of the support member, i.e., a placement surface over which toplace the powder material for three-dimensional object formation may be,for example, a smooth surface, a rough surface, a flat surface, or acurved surface. However, it is preferable that the placement surfacehave a low affinity with the organic material contained in the powdermaterial for three-dimensional object formation, when the organicmaterial is dissolved and becomes cross-linked by the effect of thecross-linking agent.

It is preferable that the affinity of the placement surface with respectto the dissolved and cross-linked organic material be lower than theaffinity of the base material with respect to the dissolved andcross-linked organic material, because this makes it easy to remove theobtained three-dimensional object from the placement surface.

—Formation of Powder Material Layer—

A method for placing the powder material for three-dimensional objectformation over the support member is not particularly limited, and anarbitrary method may be selected according to the purpose. Preferableexamples of a method for placing the powder material as a thin layerincludes a method using a publicly-known counter rolling machine (acounter roller) or the like, which is used in a selective lasersintering method described in Japanese Patent (JP-B) No. 3607300, amethod of spreading the powder material for three-dimensional objectformation into a thin layer with a member such as a brush, a roller, anda blade, a method of spreading the powder material for three-dimensionalobject formation into a thin layer by pressing the surface of the powdermaterial with a pressing member, and a method of using a publicly-knownpowder stack formation apparatus.

Placing the powder material for three-dimensional object formation as athin layer over the support member with the counter rolling machine (acounter roller), the brush or blade, the pressing member, or the likemay be practiced as follows, for example.

With the counter rolling machine (a counter roller), the brush orroller, or blade, the pressing member, or the like, the powder materialfor three-dimensional object formation is placed over the support memberthat is disposed within an outer frame (may also be referred to as“mold”, “hollow cylinder”, “tubular structure”, etc.) such that it canbe lifted up or down while sliding over the inner wall of the outerframe. In this case, when a member that can be lifted up or down withinthe outer frame is used as the support member, the support member isdisposed at a position slightly below the upper end opening of the outerframe, i.e., at a position below the upper end opening by an amountcorresponding to the thickness of the layer of the powder material forthree-dimensional object formation, and then the powder material forthree-dimensional object formation is placed over the support member. Inthis way, the powder material for three-dimensional object formation canbe placed as a thin layer over the support member.

When the hardening liquid is activated on the powder material forthree-dimensional object formation placed as a thin layer in this way,the layer is hardened (the powder material layer hardening step).

Then, when the powder material for three-dimensional object formation isplaced as a thin layer over the hardened thin layer obtained as above inthe same manner as described above, and the hardening liquid isactivated on the (layer of) the powder material for three-dimensionalobject formation placed as the thin layer, hardening occurs. Thishardening occurs not only in the (layer of) the powder material forthree-dimensional object formation placed as the thin layer, but also inthe hardened thin layer present below it and obtained through theprevious hardening. As a result, a hardened object (a three-dimensionalobject) having a thickness corresponding to about two layers of thepowder material for three-dimensional object formation placed as thethin layer is obtained.

Further, placing the powder material for three-dimensional objectformation as a thin layer over the support member can also be practicedin an automated manner easily with the publicly-known powder stackingmachine. Typically, the powder stack formation apparatus includes arecoater configured to deposit a layer of the powder material forthree-dimensional object formation, a movable supply tank configured tosupply the powder material for three-dimensional object formation overthe support member, and a movable shaping tank configured for the powdermaterial for three-dimensional object formation to be placed and stackedas a thin layer. In the powder stack formation apparatus, it is possibleto have the surface of the supply tank located slightly above thesurface of the shaping tank constantly, by lifting up the supply tank,by lifting down the shaping tank, or by both, it is possible to placethe powder material for three-dimensional object formation as a thinlayer with the recoater functioning from the supply tank side, and it ispossible to stack thin layers of the powder material forthree-dimensional object formation by repeatedly moving the recoater.

The thickness of the layer of the powder material for three-dimensionalobject formation is not particularly limited, and may be appropriatelyselected according to the purpose. However, as the average thickness perlayer, it is preferably from 30 μm to 500 μm, and more preferably form60 μm to 300 μm.

When the thickness is 30 μm or greater, a hardened object (athree-dimensional object) made of (a layer of) the powder material forthree-dimensional object formation formed by delivering the hardeningliquid to the powder material for three-dimensional object formation canhave a sufficient strength, and does not undergo problems of shapecollapse or the like during an afterward treatment or handling such assintering. When the thickness is 500 μm or less, a hardened object (athree-dimensional object) made of (a layer of) the powder material forthree-dimensional object formation formed by delivering the hardeningliquid to the powder material for three-dimensional object formation canbe enhanced in the dimensional precision.

The average thickness is not particularly limited, and can be measuredaccording to a publicly-known method.

—Powder Material Layer Hardening Step and Hardening Liquid DeliveringUnit—

The powder material layer hardening step is a step of hardening apredetermined region of the powder material layer formed in the powdermaterial layer forming step by delivering a hardening liquid containinga cross-linking agent cross-linkable with the organic material to thepowder material layer.

The hardening liquid delivering unit is a unit configured to deliver ahardening liquid containing a cross-linking agent cross-linkable withthe organic material in order to harden a predetermined region of thelayer of the powder material for three-dimensional object formationformed by the powder material layer forming unit.

The method for delivering the hardening liquid to the powder materiallayer is not particularly limited, and an arbitrary method may beselected according to the purpose. Examples thereof include a dispensermethod, a spraying method, and an inkjet method. For practicing thesemethods, a publicly-known apparatus can be favorably used as thehardening liquid delivering unit.

Among these, the dispenser method is excellent in liquid dropletquantitativity, but has a small coating coverage. The spraying methodcan form a minute discharge easily, has a wide coating coverage andexcellent coating performance, but has poor liquid dropletquantitativity, and may have the powder fly away with a sprayed flow.Therefore, the inkjet method is particularly preferable for the presentinvention. The inkjet method is preferable in that it is better than thespraying method in liquid droplet quantitativity, has a wider coatingcoverage than that of the dispenser method, and can form a complexthree-dimensional shape precisely and efficiently.

When the inkjet method is employed, the hardening liquid delivering unithas a nozzle capable of delivering the hardening liquid to the powdermaterial layer according to the inkjet method. As the nozzle, a nozzle(a discharge head) of a publicly-known inkjet printer can be favorablyused. Further, the inkjet printer can be favorably used as the hardeningliquid delivering unit. Preferable examples of the inkjet printerinclude SG7100 manufactured by Ricoh Company Limited. The inkjet printeris preferable in that it can perform coating at a high speed, because itcan drop a large amount of hardening liquid at a time, with a widecoating coverage.

In the present invention, when an inkjet printer capable of deliveringthe hardening liquid precisely at a high efficiency is used, the nozzlethereof or the head of the nozzle is not clogged or corroded, becausethe hardening liquid is free from a solid such as particles, and apolymeric high-viscosity material such as a resin. Further, when thehardening liquid is delivered (discharged) onto the layer of the powdermaterial for three-dimensional object formation, it can penetrate intothe organic material contained in the powder material forthree-dimensional object formation efficiently, resulting in anexcellent formation efficiency of a three-dimensional object. As afurther advantage, a dimensionally precise hardened object with nounexpected volume expansion or the like can be obtained easily, in ashort time, and efficiently, because no polymeric compound such as aresin is delivered.

In the hardening liquid, the cross-linking agent can also function as apH adjustor. The pH of the hardening liquid, when the hardening liquidis delivered to a layer of the powder material for three-dimensionalobject formation according to the inkjet method, is preferably from 5(mild acidic level) to 12 (basic level), and more preferably from 8 to10 (weak basic level), in terms of preventing corroding or clogging ofthe nozzle head portion of the nozzle used. For the pH adjustment, apublicly-known pH adjustor may be used.

—Powder Material Containing Unit—

The powder material containing unit is a member in which the powdermaterial for three-dimensional object formation is contained. The size,shape, material, etc, of the powder material containing unit are notparticularly limited, and may be appropriately selected according to thepurpose. Examples of the powder material containing unit include astorage tank, a bag, a cartridge, and a tank.

—Hardening Liquid Containing Unit—

The hardening liquid containing unit is a member in which the hardeningliquid is contained. The size, shape, material, etc. of the hardeningliquid containing unit are not particularly limited, and may beappropriately selected according to the purpose. Examples of thehardening liquid containing unit include a storage tank, a bag, acartridge, and a tank.

—Other Steps and Other Units—

Examples of the other steps include a drying step, a sintering step, asurface protection treatment step, and a painting step.

Examples of the other units include a drying unit, a sintering unit, asurface protection treatment unit, and a painting unit.

The drying step is a step of drying a hardened object (athree-dimensional object) obtained in the powder material layerhardening step. In the drying step, not only moisture contained in thehardened object, but also an organic substance contained therein may beremoved (wax removal). Examples of the drying unit includepublicly-known driers.

The sintering step is a step of sintering a hardened object (athree-dimensional object) formed in the powder material layer hardeningstep. Through the sintering step, the hardened object can be formed intoan integrated metal or ceramics compact (a sintered compact of thethree-dimensional object). Examples of the sintering unit includepublicly-known sintering furnaces.

The surface protection treatment step is a step of performing formation,etc, of a protection layer over the hardened object (three-dimensionalobject) formed in the powder material layer hardening step. Through thesurface protection treatment step, durability, etc. with which, forexample, the hardened object (three-dimensional object) can, as is, beserved for use, etc. can be imparted to the surface of the hardenedobject (three-dimensional object). Specific examples of the protectionlayer include a water-fast layer, a weather-fast layer, a lightfastlayer, a heat-insulating layer, and a gloss layer. Examples of thesurface protection treatment unit include publicly-known surfaceprotection treatment machines, such as a spraying machine and a coatingmachine.

The painting step is a step of painting the hardened object(three-dimensional object) formed in the powder material layer hardeningstep. Through the painting step, the hardened object (three-dimensionalobject) can be colored in a desired color. Examples of the painting unitinclude publicly-known painting machines, such as painting machines withspraying, a roller, and a brush.

FIG. 1 shows an example of a powder stack formation apparatus. Thepowder stack formation apparatus of FIG. 1 includes a formation-sidepowder storage tank 1 and a supply-side powder storage tank 2. Thesepowder storage tanks each have a stage 3 capable of moving upward anddownward, and have a thin layer made of the powder material forthree-dimensional object formation formed on the stage 3.

The apparatus includes an inkjet head 5 above the formation-side powderstorage tank 1, and a leveling machine 6 (hereinafter may be referred toas recoater). The inkjet head is configured to discharge a hardeningliquid 4 toward the powder material for three-dimensional objectformation in the formation-side powder storage tank. The levelingmachine is configured to supply the powder material forthree-dimensional object formation from the supply-side powder storagetank 2 to the formation-side powder storage tank 1, and to level off thesurface of the powder material for three-dimensional object formation inthe formation-side powder storage tank 1.

A hardening liquid 4 is dropped from the inkjet head 5 onto the powdermaterial for three-dimensional object formation in the formation-sidepowder storage tank 1. The position onto which the hardening liquid 4 isdropped is determined based on two-dimensional image data (slice data)representing a plurality of planer layers into which a three-dimensionalobject having a finally desired shape is sliced.

After image drawing on one layer is completed, the stage 3 of thesupply-side powder storage tank 2 is lifted up, and the stage 3 of theformation-side powder storage tank 1 is lifted down, which produces aheight difference. An amount of the powder material forthree-dimensional object formation corresponding to the heightdifference is moved to the formation-side powder storage tank 1 by theleveling machine 6.

In this way, one new layer of the powder material for three-dimensionalobject formation is formed over the surface of the (layer) of the powdermaterial for three-dimensional object formation over which an image hasbeen drawn before. The thickness of one layer of the powder material forthree-dimensional object formation is about from several ten μm to 100μm.

Then, an image is drawn over the newly formed layer of the powdermaterial for three-dimensional object formation, based on the slice dataof the second layer. Through repetition of this process, athree-dimensional object is obtained, and heated and dried with anunillustrated drying unit.

FIG. 2 shows another example of a powder stack formation apparatus ofthe present invention. The powder stack formation apparatus of FIG. 2 isidentical with that of FIG. 1 in principle, but is different in themechanism for supplying the powder material for three-dimensional objectformation. Specifically, the supply-side powder storage tank 2 isprovided above the formation-side powder storage tank 1. When imagedrawing over one layer is completed, the stage 3 of the formation-sidepowder storage tank 1 is lifted down by a predetermined amount, and thesupply-side powder storage tank 2 moves while dropping a predeterminedamount of the powder material for three-dimensional object formationonto the formation-side powder storage tank 1, to thereby form a newlayer of the powder material for three-dimensional object formation.After this, the leveling machine 6 compresses the powder material forthree-dimensional object formation to a higher bulk density, and levelsoff the powder material for three-dimensional object formation to auniform height at the same time.

The powder stack formation apparatus shown in FIG. 2 can be made smallerin size than the configuration of FIG. 1 in which two powder storagetanks are arranged side by side horizontally.

By means of the formation method and the formation apparatus of athree-dimensional object of the present invention, it is possible toform a three-dimensional object having a complex stereoscopic(three-dimensional (3D)) shape easily, efficiently, without causing ashape collapse before sintering, etc., and dimensionally precisely,using the powder material for three-dimensional object formation or thethree-dimensional object formation kit of the present invention.

A three-dimensional object and a sintered compact thereof that areobtained in this way have a sufficient strength and excellentdimensional precision, and can reproduce minute asperity, a curvedsurface, etc. Therefore, they are excellent in aesthetic appearance andquality, and can be favorably used for various applications.

EXAMPLES

Examples of the present invention will be explained below. The presentinvention is not limited to these Examples by any means.

—Preparation of Powder Material for Three-Dimensional Object Formation1—

—Preparation of Coating Liquid 1—

As shown in Table 1-1, unmodified partially saponified polyvinyl alcohol(PVA-205C manufactured by Kuraray Co., Ltd., with an average degree ofpolymerization of 500, and a saponification degree of 88.0 mol %) (6parts by mass), which was a water-soluble resin as the organic material(“No. 1” in Table 1-1) was mixed with water (114 parts by mass). Whilebeing heated to 80° C. in a water bus, they were stirred with athree-one motor (BL600 manufactured by Shinto Scientific Co., Ltd.) for1 hour, to dissolve the polyvinyl alcohol in the water, to therebyprepare a 5% by mass polyvinyl alcohol aqueous solution (120 parts bymass). The preparation liquid obtained in this way was a coating liquid1.

The viscosity of the 4% by mass (w/w %) polyvinyl alcohol aqueoussolution at 20° C. measured with a viscometer (a rotational viscometerDV-E VISCOMETER HADVE TYPE 115 manufactured by Brookfield EngineeringInc.) was from 5.0 mPa·s to 6.0 mPa·s as shown in Table 1-1.

—Coating of Coating Liquid 1 Over Base Material Surface—

Next, with a commercially available coating machine (MP-01 manufacturedby Powrex Corp.), the coating liquid 1 was applied to a coatingthickness (average thickness) shown in Table 1-1 to a powder ofstainless steel (SUS 316L) (PSS316L manufactured by Sanyo Special SteelCo., Ltd., with a volume average particle diameter of 41 μm) (100 partsby mass) as the base material (“No. 1” in Table 1-1). In the middle ofthis coating, the coating thickness (average thickness) and the surfacecoverage (%) of the coating liquid 1 were sampled as needed, so thatthey may become the values shown in Table 1-1 through appropriateadjustment of the coating time and interval. Through this, a powdermaterial for three-dimensional object formation 1 was obtained. Themethod for measuring the coating thickness and surface coverage, andconditions of the coating were as described below.

<Coating Thickness (Average Thickness)>

For the coating thickness (average thickness), the surface of the powdermaterial for three-dimensional object formation 1 was polished withemery paper, and then softly polished with cloth impregnated with waterto dissolve the water-soluble resin portion, to thereby produce a samplefor observation. Next, with a field-emission scanning electronmicroscope (FE-SEM), the boundary between the base material portion andthe water-soluble resin portion that was exposed was observed, and theboundary portion was measured as the coating thickness. An average of 10measurement positions was calculated as the coating thickness (averagethickness).

<Surface Coverage>

With a field-emission scanning electron microscope (FE-SEM), abackscattered electron image (ESB) was captured under the followingconditions at a viewing field setting at which about 10 particles of thepowder material for three-dimensional object formation 1 would fallwithin the range of the image. The captured image was binarized throughimage processing with IMAGEJ software. A ratio between coated portions,which were black portions, and base material portions, which were whiteportions, in one particle was calculated according to “area of blackportions/(area of black portions+area of white portions)×100”. A hundredparticles were measured, and their average was calculated as the surfacecoverage (%).

—SEM Observation Conditions—

Signal: ESB (backscattered electron image)

EHT: 0.80 kV

ESB grid: 700 V

WD: 3.0 mm

Aperture size: 30.00 μm

Contrast: 80%

Magnification: set sample by sample such that about 10 particles wouldfall horizontally in the screen.

<Coating Conditions>

Spray settings

-   -   Nozzle type: 970    -   Nozzle caliber: 1.2 mm    -   Coating liquid discharging pressure: 4.7 Pa·s    -   Coating liquid discharging rate: 3 g/min    -   Amount of air atomized: 50 NL/min

Rotor settings

-   -   Rotor type: M-1    -   Rotation speed: 60 rpm    -   Rotation number: 400%

Flow current settings

-   -   Current feeding temperature: 80° C.    -   Current feeding rate: 0.8 m³/min    -   Bag cleaning pressure of a bag filter: 0.2 MPa    -   Bag cleaning time of a bag filter: 0.3 seconds    -   Bag filter interval: 5 seconds

Coating time: 40 minutes

The average particle diameter of the obtained powder material forthree-dimensional object formation 1 measured with a commerciallyavailable particle size meter (MICROTRACK HRA manufactured by NikkisoCo, Ltd.) was 43 μm as shown in Table 2. The angle of repose of theobtained powder material, as the fluidity thereof, measured with acommercially available repose angle meter (POWDER TESTER TYPE PT-Nmanufactured by Hosokawa Micron Inc.) was 35 degrees as shown in Table2. Note that there is a tendency that the fluidity is poorer as themeasured value of the angle of repose is greater.

—Preparation of Hardening Liquid 1—

Water (70 parts by mass), 3-methyl 1,3-butanediol (manufactured by TokyoChemical Industry Co., Ltd.) (30 parts by mass) as a fluidity adjuster,and zirconium oxychloride octahydrate (zirconium oxychloridemanufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) (0.1 parts bymass) as the cross-linking agent were dispersed with a homomixer for 30minutes, to thereby prepare a hardening liquid 1 (“No. 1” in Table 1-1).

Example 1

A three-dimensional object 1 was formed in the following manner, withthe obtained powder material for three-dimensional object formation 1and the hardening liquid 1, and according to a shape printing patternhaving a size of 70 mm in length and 12 mm in width.

1) First, with a publicly-known powder stack formation apparatus asshown in FIG. 1, the powder material for three-dimensional objectformation 1 was moved from the supply-side powder storage tank to theformation-side powder storage tank, and a thin layer of the powdermaterial for three-dimensional object formation 1 having an averagethickness of 100 μm was formed over the support member.

2) Next, the hardening liquid 1 was delivered (discharged) onto thesurface of the formed thin layer of the powder material forthree-dimensional object formation 1 from a nozzle of a publicly-knowninkjet discharge head, to dissolve the polyvinyl alcohol in watercontained in the hardening liquid 1 and cross-link the polyvinyl alcoholby the effect of the cross-linking agent (zirconium oxychlorideoctahydrate) contained in the hardening liquid 1.

3) Next, hardened thin layers of the powder material forthree-dimensional object formation 1 were sequentially stacked byrepeating the operations of 1) and 2) described above until apredetermined total average thickness of 3 mm was obtained, and thensubjected to a drying step with a drier by maintaining the layers at 50°C. for 4 hours and then 100° C. for 10 hours, to thereby form athree-dimensional object 1.

The dried three-dimensional object 1 was air-blown in order for excesspowder material for three-dimensional object formation 1 to be removed.As a result, the three-dimensional object 1 did not have a shapecollapse, and had an excellent strength and dimensional precision.

The strength (hardness) and the dimensional precision were evaluatedbased on the following criteria. The results are shown in Table 2.

<Strength (Hardness)>

D—The powder material for three-dimensional object formation was nothardened sufficiently, and the three-dimensional object could not betaken out from the stacked powder material layers, and could notmaintain the predetermined shape when taken out.

C—The three-dimensional object could be taken out from the stackedpowder material layers, and it was possible to remove excess powdermaterial for three-dimensional object formation by adjusting an air blowpressure or using a brush while maintaining the shape of thethree-dimensional object.

B—When the three-dimensional object was air-blown strongly, only excesspowder material for three-dimensional object formation was removed, andthe three-dimensional object itself maintained shape.

A—The three-dimensional object was hardened sufficiently, and could notbe broken easily.

<Dimensional Precision>

D—The three-dimensional object had distortion on the surface, and whenthe surface was observed, uneven distribution of the base material andthe organic material was confirmed.

C—The three-dimensional object had slight distortion and asperity on thesurface.

B—The three-dimensional object had a favorable surface condition, buthad slight warpage.

A—The three-dimensional object had a smooth and beautiful surface, andhad no warpage.

4) The three-dimensional object 1 obtained in 3) described above wassubjected to a wax removing step with a drier by raising the temperatureup to 500° C. in 3 hours and 58 minutes, then maintaining thetemperature at 400° C. for 4 hours, and then raising the temperature to30° C. in 4 hours under a nitrogen atmosphere. Then, thethree-dimensional object 1 was sintered in a sintering furnace, undervacuum conditions, at 1,400° C. As a result, a three-dimensional object1 (a sintered compact) having a beautiful surface was obtained. Thisthree-dimensional object 1 was a completely integrated stainlessstructure (metal lump), and not at all broken when slammed to a hardfloor.

Example 2

A three-dimensional object 2 was formed in the same manner as in Example1, except that unlike in Example 1, the coating time was adjusted to 2minutes to thereby produce a powder material for three-dimensionalobject formation 2 having the average thickness and surface coverageshown in Table 1-1. The same evaluations as in Example 1 were performed.The results are shown in Table 2.

Example 3

A three-dimensional object 3 was formed in the same manner as in Example1, except that unlike in Example 1, the coating time was adjusted to 200minutes to thereby produce a powder material for three-dimensionalobject formation 3 having the average thickness and surface coverageshown in Table 1-1. The same evaluations as in Example 1 were performed.The results are shown in Table 2.

Example 4

A three-dimensional object 4 was formed in the same manner as in Example2, except that unlike in Example 2, a hardening liquid 2 was prepared byusing zirconium oxychloride octahydrate (zirconium oxychloridemanufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) (3.0 parts bymass) as a cross-linking agent. The same evaluations as in Example 1were performed. The results are shown in Table 2.

Example 5

A three-dimensional object 5 was formed in the same manner as in Example2, except that unlike in Example 2, a hardening liquid 3 was prepared byusing zirconium oxychloride octahydrate (zirconium oxychloridemanufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd) (3.5 parts bymass) as a cross-linking agent. The same evaluations as in Example 1were performed. The results are shown in Table 2.

Example 6

A three-dimensional object 6 was formed in the same manner as in Example2, except that unlike in Example 2, the water-soluble resin was changedto a polyvinyl alcohol (PVA-220C manufactured by Kuraray Co., Ltd.). Thesame evaluations as in Example 1 were performed. The results are shownin Table 2.

Example 7

A three-dimensional object 7 was formed in the same manner as in Example2, except that unlike in Example 2, the water-soluble resin was changedto a polyacrylic acid (JULIMER AC-10P manufactured by Toagosei Co.,Ltd.), the cross-linking agent was changed to aluminum hydroxide(manufactured by Wako Pure Chemical Industries, Ltd.), respectively. Thesame evaluations as in Example 1 were performed. The results are shownin Table 2.

Example 8

A three-dimensional object 8 was formed in the same manner as in Example7, except that unlike in Example 7, the water-soluble resin was changedto sodium polyacrylate (JULIMER AC-103P manufactured by Toagosei Co.,Ltd.). The same evaluations as in Example 1 were performed. The resultsare shown in Table 2.

Example 9

A three-dimensional object 9 was formed in the same manner as in Example8, except that unlike in Example 8, the cross-linking agent was changedto magnesium hydroxide (manufactured by Wako Pure Chemical Industries,Ltd.). The same evaluations as in Example 1 were performed. The resultsare shown in Table 2.

Example 10

A three-dimensional object 10 was formed in the same manner as inExample 1, except that unlike in Example 1, the water-soluble resin waschanged to an acetoacetyl group-modified polyvinyl alcohol (GOHSENXZ-300 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), andthe cross-linking agent was changed to a titanium lactate ammonium salt(ORGATIX TC-300 manufactured by Matsumoto Fine Chemical Co., Ltd.),respectively. The same evaluations as in Example 1 were performed. Theresults are shown in Table 2.

Example 11

A three-dimensional object 11 was formed in the same manner as inExample 10, except that unlike in Example 10, the water-soluble resinwas changed to a carboxyl group-modified polyvinyl alcohol (GOHSENXT-330 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.). Thesame evaluations as in Example 1 were performed. The results are shownin Table 2.

Example 12

A three-dimensional object 12 was formed in the same manner as inExample 10, except that unlike in Example 10, the water-soluble resinwas changed to a butanediol vinyl alcohol copolymer (NICHIGO G-POLYMEROKS-8041 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.).The same evaluations as in Example 1 were performed. The results areshown in Table 2.

Example 13

A three-dimensional object 13 was formed in the same manner as inExample 1, except that unlike in Example 1, the water-soluble resin waschanged to carboxymethyl cellulose sodium (CELLOGEN 5A manufactured byDaiichi Kogyo Seiyaku Co., Ltd.), and the cross-linking agent waschanged to basic aluminum acetate (manufactured by Wako Pure ChemicalIndustries, Ltd.), respectively. The same evaluations as in Example 1were performed. The results are shown in Table 2.

Example 14

A three-dimensional object 14 was formed in the same manner as inexample 13, except that unlike in Example 13, the water-soluble resinwas changed to carboxymethyl cellulose sodium (CELLOGEN 6A manufacturedby Daiichi Kogyo Seiyaku Co., Ltd.). The same evaluations as in example1 were performed. The results are shown in Table 2.

Example 15

A three-dimensional object 15 was formed in the same manner as inExample 1, except that unlike in Example 1, the water-soluble resin waschanged to starch (HISTARD PSS-5 manufactured by Sanwa Starch Co.,Ltd.), and the cross-linking agent was changed to a bis vinyl sulfonecompound (VS-B (K-FJC) manufactured by Fuji Fine Chemical Co., Ltd.),respectively. The same evaluations as in example 1 were performed. Theresults are shown in Table 2.

Example 16

A three-dimensional object 16 was formed in the same manner as inExample 15, except that unlike in Example 15, the water-soluble resinwas changed to gelatin (BEMATRIX GELATIN manufactured by Nitta GelatinInc.). The same evaluations as in Example 1 were performed. The resultsare shown in Table 2.

Example 17

A three-dimensional object 17 was formed in the same manner as inExample 1, except that unlike in Example 1, the base material waschanged to stainless steel (SUS 316L) (PSS316L (a product with a volumeaverage particle diameter of 20 μm or less), manufactured by SanyoSpecial Steel Co., Ltd.). The same evaluations as in Example 1 wereperformed. The results are shown in Table 2.

Example 18

A three-dimensional object 18 was formed in the same manner as inExample 1, except that unlike in Example 1, the base material waschanged to silica (ECCERICA SE-15 manufactured by Tokuyama Corporation,with a volume average particle diameter of 24 μm). The same evaluationsas in Example 1 were performed. The results are shown in Table 2.

Example 19

A three-dimensional object 19 was formed in the same manner as inExample 1, except that unlike in Example 1, the base material waschanged to alumina (TAIMICRON TM-5D manufactured by Taimei ChemicalsCo., Ltd., with a volume average particle diameter of 0.3 μm). The sameevaluations as in Example 1 were performed. The results are shown inTable 2.

Example 20

A three-dimensional object 20 was formed in the same manner as inExample 1, except that unlike in Example 1, the base material waschanged to zirconia (TZ-B53 manufactured by Tosoh Corporation, with avolume average particle diameter of 50 μm). The same evaluations as inExample 1 were performed. The results are shown in Table 2.

Example 21

Unlike in Example 1, a powder material for three-dimensional objectformation was produced by changing the base material to stainless steel(SUS 316L) (PSS316L (a product with a volume average particle diameterof 20 μm or less), manufactured by Sanyo Special Steel Co., Ltd.). Afterthis, the produced powder material for three-dimensional objectformation was classified with a sonic sieve shaker SW-20A (manufacturedby Tsutsui Scientific Instruments, Co., Ltd.), and particles havingpassed through a sieve aperture size of 5 μm were collected. Thecollected particles were used as a powder material for three-dimensionalobject formation 18.

A three-dimensional object 21 was formed in the same manner as inExample 1 with the use of the obtained powder material forthree-dimensional object formation 18, and the same evaluations as inExample 1 were performed. The results are shown in Table 2.

Example 22

Unlike in Example 1, a powder material for three-dimensional objectformation was produced by changing the base material to stainless steel(SUS 316L) (PSS316L (a product with a volume average particle diameterof 20 μm or less), manufactured by Sanyo Special Steel Co., Ltd.). Afterthis, the produced powder material for three-dimensional objectformation was classified with a sonic sieve shaker SW-20A (manufacturedby Tsutsui Scientific Instruments, Co., Ltd.), and particles havingpassed through a sieve aperture size of 10 μm were collected. Thecollected particles were used as a powder material for three-dimensionalobject formation 19.

A three-dimensional object 22 was formed in the same manner as inExample 1 with the use of the obtained powder material forthree-dimensional object formation 19, and the same evaluations as inExample 1 were performed. The results are shown in Table 2.

Example 23

A powder material for three-dimensional object formation 20 was producedin the same manner as in Example 1, except that unlike in Example 1, thebase material was changed to stainless steel (SUS 316L) (PSS 316L (aproduct with a volume average particle diameter of 10 μm or less),manufactured by Sanyo Special Steel Co., Ltd.).

A three-dimensional object 23 was formed in the same manner as inExample 1 with the use of the obtained powder material forthree-dimensional object formation 20, and the same evaluations as inExample 1 were performed. The results are shown in Table 2.

Comparative Example 1

A three-dimensional object 24 was formed in the same manner as inExample 1, except that unlike in Example 1, no cross-linking agent wasused. The same evaluations as in Example 1 were performed. The resultsare shown in Table 2.

TABLE 1-1 Powder material for three-dimensional object formationHardening Base Organic material Ave. liquid material Viscosity thicknessSurface Crosslinking No. No. Kind No. Kind (mPa · s) (nm) coverage No.agent Ex. 1 1 1 SUS 1 Polyvinyl 5.0-6.0 100 100% 1 zirconium 316Lalcohol oxy- chloride octa- hydrate Ex. 2 2 1 SUS 1 Polyvinyl 5.0-6.0 515% 1 zirconium 316L alcohol oxy- chloride octa- hydrate Ex. 3 3 1 SUS 1Polyvinyl 5.0-6.0 500 100% 1 zirconium 316L alcohol oxy- chloride octa-hydrate Ex. 4 2 1 SUS 1 Polyvinyl 5.0-6.0 5 15% 2 zirconium 316L alcoholoxy- chloride octa- hydrate Ex. 5 2 1 SUS 1 Polyvinyl 5.0-6.0 5 15% 3zirconium 316L alcohol oxy- chloride octa- hydrate Ex. 6 4 1 SUS 2Polyvinyl 29.0-35.0 5 15% 1 zirconium 316L alcohol oxy- chloride octa-hydrate Ex. 7 5 1 SUS 3 Poly- 1.0-3.0 100 100% 4 Aluminum 316L acrylichydroxide acid Ex. 8 6 1 SUS 4 Sodium 3.0-5.0 100 100% 4 Aluminum 316Lpoly- hydroxide acrylate Ex. 9 6 1 SUS 4 Sodium 3.0-5.0 100 100% 5Magnesium 316L poly- hydroxide acrylate

TABLE 1-2 Powder material for three-dimensional object formationHardening Base Organic material Ave. liquid material Viscosity thicknessSurface Crosslinking No. No. Kind No. Kind (mPa · s) (nm) coverage No.agent Ex. 10 7 1 SUS 5 Aceto 24.0-30.0 100 100% 6 Titanium 316L acetyllactate group- ammonium modified salt polyvinyl alcohol Ex. 11 8 1 SUS 6Carboxyl 27.0-33.0 100 100% 6 Titanium 316L group- lactate modifiedammonium polyvinyl salt alcohol Ex. 12 9 1 SUS 7 Butane 3.0 100 100% 6Titanium 316L diol vinyl lactate alcohol ammonium copolymer salt Ex. 1310 1 SUS 8 Carboxy 10.0-15.0 100 100% 7 Basic 316L methyl aluminumcellulose acetate sodium Ex. 14 11 1 SUS 9 Carboxy 35.0-40.0 100 100% 7Basic 316L methyl aluminum cellulose acetate sodium Ex. 15 12 1 SUS 10Starch 6.0 100 100% 8 Bis 316L vinyl sulfone compound Ex. 16 13 1 SUS 11Gelatin 10.0  100 100% 8 Bis 316L vinyl sulfone compound Ex. 17 14 2 SUS1 Polyvinyl 5.0-6.0 100 100% 1 zirconium 316L alcohol oxy- chlorideocta- hydrate Ex. 18 15 3 SiO₂ 1 Polyvinyl 5.0-6.0 100 100% 1 zirconiumalcohol oxy- chloride octa- hydrate

TABLE 1-3 Powder material for three-dimensional object formationHardening Base Organic material Ave. liquid material Viscosity thicknessSurface Crosslinking No. No. Kind No. Kind (mPa · s) (nm) coverage No.agent Ex. 19 16 4 Al₂O₃ 1 Polyvinyl 5.0-6.0 100 100% 1 zirconium alcoholoxy- chloride octa- hydrate Ex. 20 17 5 ZrO₂ 1 Polyvinyl 5.0-6.0 100100% 1 zirconium alcohol oxy- chloride octa- hydrate Ex. 21 18 6 SUS 1Polyvinyl 5.0-6.0 100 100% 1 zirconium 316L alcohol oxy- chloride octa-hydrate Ex. 22 19 7 SUS 1 Polyvinyl 5.0-6.0 100 100% 1 zirconium 316Lalcohol oxy- chloride octa- hydrate Ex. 23 20 8 SUS 1 Polyvinyl 5.0-6.0100 100% 1 zirconium 316L alcohol oxy- chloride octa- hydrate Comp. 1 1SUS 1 Polyvinyl 5.0-6.0 100 100% none — Ex. 1 316L alcohol

TABLE 2 Powder material for three-dimensional Three-dimensional objectobject formation fluidity evaluations Ave. particle Angle of DimensionalNo. diameter (μm) repose (deg) Strength precision Ex. 1 1 43 35 B B Ex.2 2 43 32 C A Ex. 3 3 88 42 A C Ex. 4 2 43 32 A B Ex. 5 2 43 32 A B Ex.6 4 125 37 A B Ex. 7 5 43 33 B B Ex. 8 6 43 36 B B Ex. 9 6 43 36 C B Ex.10 7 116 39 A B Ex. 11 8 155 40 A B Ex. 12 9 43 31 A B Ex. 13 10 85 30 BB Ex. 14 11 220 41 B C Ex. 15 12 43 33 C B Ex. 16 13 43 33 C B Ex. 17 1415 45 B A Ex. 18 15 15 36 B A Ex. 19 16 250 42 B C Ex. 20 17 48 33 B BEx. 21 18 3 46 A C Ex. 22 19 5 45 A B Ex. 23 20 10 45 A B Comp. 1 43 35D A Ex. 1—Preparation of Power Material for Three-Dimensional Object Formation101——Preparation of Coating Liquid 101—

As shown in Table 3-1, an acetoacetyl group-modified polyvinyl alcohol(GOHSENX Z-100 manufactured by Nippon Synthetic Chemical Industry Co.,Ltd., with an average degree of polymerization of 500, and asaponification degree of 98.5 mol %) (6 parts by mass), which was awater-soluble resin, was mixed with water (114 parts by mass). Whilebeing heated to 90° C. in a water bus, they were stirred with athree-one motor (BL600 manufactured by Shinto Scientific Co., Ltd.) for1 hour, to dissolve the acetoacetyl group-modified polyvinyl alcohol inthe water, to thereby prepare a 5% by mass acetoacetyl group-modifiedpolyvinyl alcohol aqueous solution (120 parts by mass). The preparationliquid obtained in this way was a coating liquid 101.

The viscosity of the 4% by mass (w/w %) acetoacetyl group-modifiedpolyvinyl alcohol aqueous solution at 20° C., measured with a viscometer(a rotational viscometer DV-E VISCOMETER HADVE TYPE 115 manufactured byBrookfield Engineering Inc.), was from 5.0 mPa·s to 6.0 mPa·s, as shownin Table 3-1.

—Coating of Coating Liquid 101 Over Base Material Surface—

Next, with a commercially available coating machine (MP-01 manufacturedby Powrex Corp.), the coating liquid 101 was applied to a coatingthickness (average thickness) shown in Table 3-1 to a powder ofstainless steel (SUS 316L) (PSS316L manufactured by Sanyo Special SteelCo., Ltd., with a volume average particle diameter of 41 μm) (100 partsby mass) as the base material (“No. 101” in Table 3-1). In the middle ofthis coating, the coating thickness (average thickness) and the surfacecoverage (%) of the coating liquid 101 were sampled as needed, so thatthey may become the values shown in Table 3-1 through appropriateadjustment of the coating time and interval. Through this, a powdermaterial for three-dimensional object formation 101 was obtained. Themethod for measuring the coating thickness and surface coverage was thesame as that for the powder material 1 for three-dimensional objectformation, and conditions of the coating were as described below.

<Coating Conditions>

Spray settings

-   -   Nozzle type: 970    -   Nozzle caliber: 1.2 mm    -   Coating liquid discharging pressure: 4.7 Pa·s    -   Coating liquid discharging rate: 3 g/min    -   Amount of air atomized: 50 NL/min

Rotor settings

-   -   Rotor type: M-1    -   Rotation speed: 60 rpm    -   Rotation number: 400%

Flow current settings

-   -   Current feeding temperature: 80° C.    -   Current feeding rate: 0.8 m³/min    -   Bag cleaning pressure of a bag filter: 0.2 MPa    -   Bag cleaning time of a bag filter: 0.3 seconds    -   Bag filter interval: 5 seconds

Coating time: 160 minutes

—Preparation of Hardening Liquid 101—

Water (70 parts by mass), 3-methyl 1,3-butanediol (manufactured by TokyoChemical Industry Co., Ltd.) (30 parts by mass) as a fluidity adjuster,and an ammonium zirconium carbonate salt (ZIRCOZOL AC-20 manufactured byDaiichi Kigenso Kagaku Kogyo Co., Ltd.) (5 parts by mass) as thecross-linking agent were mixed and dissolved, to thereby prepare ahardening liquid 101.

Example 24

A three-dimensional object 101 was formed in the following manner, withthe obtained powder material for three-dimensional object formation 101,the hardening liquid 101, and a shape printing pattern having a size of70 mm in length and 12 mm in width.

1) First, with a publicly-known powder stack formation apparatus asshown in FIG. 1, the powder material for three-dimensional objectformation 101 was moved from the supply-side powder storage tank to theformation-side powder storage tank, and a thin layer of the powdermaterial for three-dimensional object formation 101 having an averagethickness of 100 μm was formed over the support member.

2) Next, the hardening liquid 101 was delivered (discharged) onto thesurface of the formed thin layer of the powder material forthree-dimensional object formation 101 from a nozzle of a publicly-knowninkjet discharge head, to dissolve the acetoacetyl group-modifiedpolyvinyl alcohol in water contained in the hardening liquid 101 andcross-link the acetoacetyl group-modified polyvinyl alcohol by theeffect of the cross-linking agent (ammonium zirconium carbonate salt)contained in the hardening liquid 101.

3) Next, hardened thin layers of the powder material forthree-dimensional object formation 101 were sequentially stacked byrepeating the operations of 1) and 2) described above until apredetermined total average thickness of 3 mm was obtained, and thensubjected to a drying step with a drier by maintaining the layers at 50°C. for 4 hours and then 100° C. for 10 hours, to thereby form athree-dimensional object 101.

The dried three-dimensional object 101 was air-blown in order for excesspowder material for three-dimensional object formation 101 to beremoved. As a result, the three-dimensional object 101 did not have ashape collapse, and had an excellent strength and dimensional precision.

The strength (hardness) and the dimensional precision of the obtainedthree-dimensional object 101 were evaluated in the same manner as inExample 1 described above. Further, a bending stress of thethree-dimensional object 101 was measured in the manner described below.The results are shown in Table 4.

<Bending Stress>

A three-point bending stress (MPa) of the obtained three-dimensionalobject 101 was measured with an autograph AGS-J and a three-pointbending test jig (plastic) manufactured by Shimadzu Corporation. Thebending stress was evaluated based on the criteria below.

[Evaluation Criteria]

A: 8.0 MPa or greater

B: 5.0 MPa or greater but less than 8.0 MPa

C: 3.0 MPa or greater but less than 5.0 MPa

D: Less than 3.0 MPa

4) The three-dimensional object 101 obtained in 3) described above wassubjected to a wax removing step with a drier by raising the temperatureup to 500° C. in 3 hours and 58 minutes, then maintaining thetemperature at 400° C. for 4 hours, and then raising the temperature to30° C. in 4 hours under a nitrogen atmosphere. Then, thethree-dimensional object 101 was sintered in a sintering furnace, undervacuum conditions, at 1,400° C. As a result, a three-dimensional object101 (a sintered compact) having a beautiful surface was obtained. Thisthree-dimensional object 101 was a completely integrated stainlessstructure (metal lump), and not at all broken when slammed to a hardfloor.

Example 25

A three-dimensional object 102 was formed in the same manner as inExample 24, except that unlike in Example 24, the coating time wasadjusted to 80 minutes to thereby produce a powder material forthree-dimensional object formation 102 having the average thickness andsurface coverage shown in Table 3-1. The same evaluations as in Example24 were performed. The results are shown in Table 4.

Example 26

A three-dimensional object 103 was formed in the same manner as inExample 24, except that unlike in Example 24, the coating time wasadjusted to 320 minutes to thereby produce a powder material forthree-dimensional object formation 103 having the average thickness andsurface coverage shown in Table 3-1. The same evaluations as in Example24 were performed. The results are shown in Table 4.

Example 27

A three-dimensional object 104 was formed in the same manner as inExample 24, except that unlike in Example 24, a glyoxylic acid salt(SAFELINK SPM-01 manufactured by Nippon Synthetic Chemical Industry Co.,Ltd.) (3.0 parts by mass) was used as a cross-linking agent to therebyprepare a hardening liquid 102. The same evaluations as in Example 24were performed. The results are shown in Table 4.

Example 28

A three-dimensional object 105 was formed in the same manner as inExample 25 except that unlike in Example 25, adipic dihydrazide(manufactured by Otsuka Chemical Co., Ltd.) (3.5 parts by mass) was usedas a cross-linking agent to thereby prepare a hardening liquid 103. Thesame evaluations as in Example 24 were performed. The results are shownin Table 4.

Example 29

A three-dimensional object 106 was formed in the same manner as inExample 25, except that unlike in Example 25, the water-soluble resinwas changed to an acetoacetyl group-modified polyvinyl alcohol (GOHSENXZ-200 manufactured by Nippon Synthetic Chemical Industry Co., Ltd., withan average degree of polymerization of 1,000, and a saponificationdegree of 99.0 mol %), the coating liquid concentration was changed to3% by mass, and the coating time was adjusted to 133 minutes. The sameevaluations as in Example 24 were performed. The results are shown inTable 4.

Example 30

A three-dimensional object 107 was formed in the same manner as inExample 25, except that unlike in Example 25, the water-soluble resinwas changed to an acetoacetyl group-modified polyvinyl alcohol (GOHSENXZ-210 manufactured by Nippon Synthetic Chemical Industry Co., Ltd., withan average degree of polymerization of 1,000, and a saponificationdegree of 95.5 mol %), the coating liquid concentration was changed to3% by mass, and the coating time was adjusted to 133 minutes. The sameevaluations as in Example 24 were performed. The results are shown inTable 4.

Example 31

A three-dimensional object 108 was formed in the same manner as inExample 25, except that unlike in Example 25, the water-soluble resinwas changed to an acetoacetyl group-modified polyvinyl alcohol (GOHSENXZ-220 manufactured by Nippon Synthetic Chemical Industry Co., Ltd., withan average degree of polymerization of 1,000, and a saponificationdegree of 90.8 mol %), the coating liquid concentration was changed to3% by mass, and the coating time was adjusted to 133 minutes. The sameevaluations as in Example 24 were performed. The results are shown inTable 4.

Example 32

A three-dimensional object 109 was formed in the same manner as inExample 25, except that unlike in Example 25, the water-soluble resinwas changed to an acetoacetyl group-modified polyvinyl alcohol (GOHSENXZ-300 manufactured by Nippon Synthetic Chemical Industry Co., Ltd., withan average degree of polymerization of 1,700, and a saponificationdegree of 99.0 mol %), the coating liquid concentration was changed to3% by mass, and the coating time was adjusted to 133 minutes. The sameevaluations as in Example 24 were performed. The results are shown inTable 4.

Example 33

A three-dimensional object 110 was formed in the same manner as inExample 24, except that unlike in Example 24, zirconium lactate ammoniumsalt (ORGATIX ZC-300 manufactured by Matsumoto Fine Chemical Co., Ltd.)(5 parts by mass) was used as the cross-linking agent to thereby preparea hardening liquid 104. The same evaluations as in Example 24 wereperformed. The results are shown in Table 4.

Example 34

A three-dimensional object 111 was formed in the same manner as inExample 25, except that unlike in Example 25, zirconium lactate ammoniumsalt (ORGATIX ZC-300 manufactured by Matsumoto Fine Chemical Co., Ltd.)(5 parts by mass) was used as the cross-linking agent to thereby preparea hardening liquid 104. The same evaluations as in Example 24 wereperformed. The results are shown in Table 4.

Example 35

A three-dimensional object 112 was formed in the same manner as inExample 26, except that unlike in Example 26, zirconium lactate ammoniumsalt (ORGATIX ZC-300 manufactured by Matsumoto Fine Chemical Co., Ltd.)(5 parts by mass) was used as the cross-linking agent to thereby preparea hardening liquid 104. The same evaluations as in Example 24 wereperformed. The results are shown in Table 4.

Example 36

A three-dimensional object 113 was formed in the same manner as inExample 34, except that unlike in Example 34, the water-soluble resinwas changed to a carboxyl group-modified polyvinyl alcohol (GOHSENXT-330 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), thecoating liquid concentration was changed to 3% by mass, and the coatingtime was adjusted to 133 minutes. The same evaluations as in Example 24were performed. The results are shown in Table 4.

Example 37

A three-dimensional object 114 was formed in the same manner as inExample 34, except that unlike in Example 34, the water-soluble resinwas changed to a non-modified partially-saponified polyvinyl alcohol(PVA-205C manufactured by Kuraray Co., Ltd., with an average degree ofpolymerization of 500, and a saponification degree of 88.0 mol %). Thesame evaluations as in Example 24 were performed. The results are shownin Table 4.

Comparative Example 2

A three-dimensional object 115 was formed in the same manner as inExample 25, except that unlike in example 25, no cross-linking agent wasused. The same evaluations as in Example 24 were performed. The resultsare shown in Table 4.

Comparative Example 3

A three-dimensional object 116 was formed in the same manner as inExample 25, except that the cross-linking agent was changed from theammonium zirconium carbonate salt (ZIRCOZOL AC-20 manufactured byDaiichi Kigenso Kagaku Kogyo Co., Ltd.) of Example 25 to dialkylperoxide (KAYABUTYL C manufactured by Kayaku Akzo Corporation) tothereby prepare a hardening liquid 105. The same evaluations as inExample 24 were performed. The results are shown in Table 4.

TABLE 3-1 Powder material for three-dimensional object formationHardening Base Organic material Ave. liquid material Viscosity thicknessSurface Crosslinking No. No. Kind No. Kind (mPa · s) (nm) coverage No.agent Ex. 24 101 101 SUS 101 Aceto 5.0-6.0 400 100% 101 Ammonium 316Lacetyl zirconium group- carbonate modified salt polyvinyl alcohol Ex. 25102 101 SUS 101 Aceto 5.0-6.0 200 100% 101 Ammonium 316L acetylzirconium group- carbonate modified salt polyvinyl alcohol Ex. 26 103101 SUS 101 Aceto 5.0-6.0 800 100% 101 Ammonium 316L acetyl zirconiumgroup- carbonate modified salt polyvinyl alcohol Ex. 27 101 101 SUS 101Aceto 5.0-6.0 400 100% 102 Glyoxylic 316L acetyl acid salt group-modified polyvinyl alcohol Ex. 28 102 101 SUS 101 Aceto 5.0-6.0 200 100%103 Adipic 316L acetyl dihydrazide group- modified polyvinyl alcohol Ex.29 104 101 SUS 102 Aceto 11.5-15.0 200 100% 101 Ammonium 316L acetylzirconium group- carbonate modified salt polyvinyl alcohol Ex. 30 105101 SUS 103 Aceto 11.5-15.0 200 100% 101 Ammonium 316L acetyl zirconiumgroup- carbonate modified salt polyvinyl alcohol Ex. 31 106 101 SUS 104Aceto 11.5-15.0 200 100% 101 Ammonium 316L acetyl zirconium group-carbonate modified salt polyvinyl alcohol

TABLE 3-2 Powder material for three-dimensional object formationHardening Base Organic material Ave. liquid material Viscosity thicknessSurface Crosslinking No. No. Kind No. Kind (mPa · s) (nm) coverage No.agent Ex. 32 107 101 SUS 105 Aceto 24.0-30.0 200 100% 101 Ammonium 316Lacetyl zirconnium group- carbonate modified salt polyvinyl alcohol Ex.33 101 101 SUS 101 Aceto 5.0-6.0 400 100% 104 Zirconium 316L acetyllactate group- ammonium modified salt polyvinyl alcohol Ex. 34 102 101SUS 101 Aceto 5.0-6.0 200 100% 104 Zirconium 316L acetyl lactate group-ammonium modified salt polyvinyl alcohol Ex. 35 103 101 SUS 101 Aceto5.0-6.0 800 100% 104 Zirconium 316L acetyl lactate group- ammoniummodified salt polyvinyl alcohol Ex. 36 108 101 SUS 101 Carboxyl27.0-33.0 200 100% 104 Zirconium 316L group lactate modified ammoniumpolyvinyl salt alcohol Ex. 37 109 101 SUS 101 Partially- 5.0-6.0 200100% 104 Zirconium 316L saponified lactate polyvinyl ammonium alcoholsalt Comp. 102 101 SUS 101 Aceto 5.0-6.0 200 100% — None Ex. 2 316Lacetyl group- modified polyvinyl alcohol Comp. 102 101 SUS 101 Aceto5.0-6.0 200 100% 105 Dialkyl Ex. 3 316L acetyl peroxide group- modifiedpolyvinyl alcohol

TABLE 4 Powder material for three-dimensional object formationThree-dimensional Ave. fluidity object evaluations particle Angle ofDimen- Bending diameter repose sional stress No. (μm) (deg) Strengthprecision (Mpa) Ex. 24 101 48 35 A A A Ex. 25 102 47 34 A A B Ex. 26 10349 37 A B A Ex. 27 101 48 36 A B C Ex. 28 102 47 32 A B C Ex. 29 104 4834 A B B Ex. 30 105 48 33 A B B Ex. 31 106 48 37 A B B Ex. 32 107 100 39A B C Ex. 33 101 48 35 A A B Ex. 34 102 47 34 A A C Ex. 35 103 49 37 A BA Ex. 36 108 40 34 A B C Ex. 37 109 38 37 B B C Comp. 102 47 35 D D DEx. 2 Comp. 102 47 34 D D D Ex. 3

Examples 38 to 40

Discharging stability (storage stability test) of the hardening liquids6, 101, and 104 described above was evaluated based on the criteriadescribed below. The results are shown in Table 5.

<Storage Stability Test on Hardening Liquid>

A hundred droplets of each of the hardening liquids were discharged from50 nozzles of an inkjet discharge head (with a nozzle diameter of 28μ),and after this, the ink discharge head was left under a 50° C. conditionfor 1 month with the nozzles capped. Storage stability of each hardeningliquid was evaluated based on the number of times of cleaning operationsrequired until the discharging condition of each hardening liquid afterleft under that condition was returned to the initial dischargingcondition.

[Evaluation Criteria]

D: The initial discharging condition was not recovered with 4 or moretimes of cleaning operations.

C: The initial discharging condition was recovered with 3 times ofcleaning operations.

B: The initial discharging condition was recovered with 2 times ofcleaning operations.

A: The initial discharging condition was recovered with 1 time ofcleaning operation.

Comparative Example 4

Discharging stability (storage stability test) of the hardening liquid105 described above was evaluated in the same manner as in Examples 38to 40. The result is shown in Table 5.

TABLE 5 Hardening liquid No. Cross-linking agent Storage stability Ex.38 6 Titanium lactate ammonium salt A Ex. 39 101 Ammonium zirconiumcarbonate salt C Ex. 40 104 Zirconium lactate ammonium salt A Comp. 105Dialkyl peroxide (KAYABUTYL C) D Ex. 4

Aspects of the present invention are as follows, for example.

<1> A three-dimensional object formation method, including forming athree-dimensional object by at least repeating:

forming a powder material layer using a powder material forthree-dimensional object formation containing a base material coatedwith an organic material; and

hardening a predetermined region of the powder material layer bydelivering a hardening liquid to the powder material layer formed in theformation of a powder material layer, where the hardening liquidcontains a cross-linking agent cross-linkable with the organic material.

<2> The three-dimensional object formation method according to <1>,

wherein the cross-linking agent is any of a water-soluble organiccross-linking agent and a metal salt.

<3> The three-dimensional object formation method according to <2>,

wherein the metal salt ionizes a divalent or higher cationic metal inwater.

<4> The three-dimensional object formation method according to <3>,

wherein a lactic acid ion is coordinated to the cationic metal.

<5> The three-dimensional object formation method according to any oneof <1> to <4>,

wherein a coverage of a surface of the base material with the organicmaterial is 15% or higher.

<6> The three-dimensional object formation method according to any oneof <1> to <5>,

wherein a 4% by mass (w/w %) solution of the organic material has aviscosity of 40 mPa·S or lower at 20° C.

<7> The three-dimensional object formation method according to any oneof <1> to <6>,

wherein the organic material is a water-soluble resin.

<8> The three-dimensional object formation method according to <7>,

wherein the water-soluble resin contains a polyvinyl alcohol resin.

<9> The three-dimensional object formation method according to <8>,

wherein the polyvinyl alcohol resin is an acetoacetyl group-modifiedpolyvinyl alcohol resin.

<10> The three-dimensional object formation method according to <8> or<9>,

wherein the polyvinyl alcohol resin has an average degree ofpolymerization of from 400 to 1,100.

<11> The three-dimensional object formation method according to any oneof <1> to <10>,

wherein the powder material for three-dimensional object formation hasan average particle diameter of from 3 μm to 250 μm.

<12> The three-dimensional object formation method according to any oneof <1> to <11>,

wherein the base material is metal particles, or ceramics particles, orboth.

<13> The three-dimensional object formation method according to any oneof <1> to <12>, further including:

sintering the three-dimensional object formed by repeating the formationof a powder material layer and the hardening.

<14> The three-dimensional object formation method according to any oneof <1> to <13>,

wherein the delivering of the hardening liquid is performed according toan inkjet method.

<15> A powder material for three-dimensional object formation,

wherein the powder material for three-dimensional object formation isused in the three-dimensional object formation method according to anyone of <1> to <14>, and contains the base material coated with theorganic material.

<16> A hardening liquid,

wherein the hardening liquid is used in the three-dimensional objectformation method according to any one of <1> to <14>, and contains thecross-linking agent cross-linkable with the organic material.

<17> A three-dimensional object formation kit, including:

the powder material for three-dimensional object formation according to<15>; and

the hardening liquid according to <16>.

<18> A three-dimensional object formation apparatus, including:

a powder material layer forming unit configured to form a layer of apowder material for three-dimensional object formation containing a basematerial coated with an organic material;

a hardening liquid delivering unit configured to deliver a hardeningliquid containing a cross-linking agent cross-linkable with the organicmaterial, in order to harden a predetermined region of the layer of thepowder material for three-dimensional object formation formed by thepowder material layer forming unit;

a powder material containing unit containing the powder material forthree-dimensional object formation; and

a hardening liquid containing unit containing the hardening liquid.

REFERENCE SIGNS LIST

-   -   1 formation-side powder storage tank    -   2 supply-side powder storage tank    -   3 stage    -   4 hardening liquid    -   5 inkjet head    -   6 leveling machine

The invention claimed is:
 1. A three-dimensional object formationmethod, comprising: forming a powder material layer comprising a powdermaterial for three-dimensional object formation, the powder materialcomprising a particle which comprises: a base material, which is a metalparticle, a ceramic particle, or both; and an organic material providedon a surface of the base material, and having a thickness of from 5 to300 nm, wherein the surface of the base material is covered with theorganic material at a coverage of 50% by area or greater, and whereinthe organic material is an organic resin; delivering a hardening liquidby discharging to the powder material layer formed in the formation of apowder material layer, where the hardening liquid comprises across-linking agent containing a site cross-linkable with across-linkable functional group of the organic material, wherein theorganic material is dissolved and cross-linked by an effect of thecross-linking agent; hardening a predetermined region of the powdermaterial layer, and repeating the forming of the powder material layer,the delivering of the hardening liquid and the hardening of thepredetermined region of the powder material layer, to form athree-dimensional object.
 2. The three-dimensional object formationmethod according to claim 1, wherein the cross-linking agent is at leastone selected from the group consisting of a water-soluble organiccross-linking agent and a metal salt.
 3. The three-dimensional objectformation method according to claim 2, wherein the cross-linking agentis the metal salt, and the metal salt comprises a divalent or highercationic metal which ionizes in water.
 4. The three dimensional objectformation method according to claim 3, wherein the metal salt comprisesa lactic acid ion, which is coordinated to the cationic metal in water.5. The three-dimensional object formation method according to claim 1,wherein a 4% by mass (w/w %) solution of the organic material in asolvent of the hardening liquid has a viscosity of 40 mPa·s or lower at20° C.
 6. The three-dimensional object formation method according toclaim 1, wherein the organic material is a water-soluble resin.
 7. Thethree-dimensional object formation method according to claim 6, whereinthe water-soluble resin comprises a polyvinyl alcohol resin.
 8. Thethree-dimensional object formation method according to claim 7, whereinthe polyvinyl alcohol resin is an acetoacetyl group-modified polyvinylalcohol resin.
 9. The three-dimensional object formation methodaccording to claim 7, wherein the polyvinyl alcohol resin has an averagedegree of polymerization of from 400 to 1,100.
 10. The three-dimensionalobject formation method according to claim 1, wherein the powdermaterial for three-dimensional object formation has an average particlediameter of from 3 μm to 250 μm.
 11. The three-dimensional objectformation method according to claim 1, further comprising: sintering thethree-dimensional object formed by the repeating of the forming of thepowder material layer, the delivering of the hardening liquid and thehardening of the predetermined region of the powder material layer. 12.The three-dimensional object formation method according to claim 1,wherein the delivering of the hardening liquid is performed with aninkjet method.
 13. The three-dimensional object formation methodaccording to claim 1, wherein an amount of the cross-linking agent isfrom 0.1 parts by mass to 5 parts by mass relative to 100 parts by massof the hardening liquid.
 14. The three-dimensional object formationmethod according to claim 1, wherein the organic material is at leastone selected from the group consisting of an acrylic resin, a maleicacid resin, a butyral resin, an epoxy resin, and a polyvinyl butyralresin.